This invention relates to the representation of class associations within a class inheritance hierarchy.
A collection of resources or components within a system can typically be represented as a hierarchy of objects. Such a representation can be helpful for management, for example for remote management of part or all of the system.
The Simple Network Management Protocol (SNMP) provides a means for monitoring and managing systems remotely via a network. More information on SNMP can be found in RFC2576 and RFC2578 from the Internet Engineering Task Force (IETF). Nodes of a system managed under SNMP have an associated SNMP agent that interfaces with a management interface at the node via the SNMP protocol and exposes portions of the node's management interfaces to SNMP managers on the network. The representation of this information is defined in a Management Information Base (MIB) specified using a notation known as the Structure of Management Information, the definition of version 2 of which may also be obtained from the IETF.
The system/devices that are represented by the MIB are viewed as a collection of managed objects, each of which may be said to be of a given object class. The attributes of multiple instances of such a class are generally represented within the MIB using SNMP tables.
The Telecommunications Management Network (TNM) network management model defines a class hierarchy of such managed object classes. However, SNMP does not provide a mechanism for presenting instances of classes from within such an inheritance hierarchy. SNMP tables do not provide a structure whereby the hierarchical relationships can be represented. A consequential disadvantage of this is that the conventional tabular approach of SNMP provides for only limited extensibility, and the structure of the tables is inflexible.
A co-pending U.S. application Ser. No. 09/796,931, filed Feb. 28, 2001, assigned to the present assignee, describes a computer-implemented method and apparatus that can represent system management information for components of the system as instances of object classes within a defined inheritance hierarchy. The class inheritance hierarchy can include multiple levels below an object class including at least a first level below the object class and a second level below the first level. A first level object class at the first level can form an instance of the class and a second level object class at the second level can form an instance at the first level object class. Each instance of an object class can have an attribute with a value representing a characteristic of that instance of the object class. The method and apparatus can involve populating a plurality of tables, the tables being allocated to respective object classes at the multiple levels. The tables can be populated with instance entries for instances of the object classes to which the tables are allocated. The instance entries in the tables can be populated with attribute entries for an attribute of the object classes. The allocation of attributes to the attribute entries can be effected so as to mirror the class inheritance hierarchy. Attributes common to multiple instances of a predetermined object class can be held in the table for that object class. This approach can be applied throughout the object hierarchy. The class can be represented in a Management Information Base (MIB) table with the classes at lower levels in the hierarchy being represented by respective extension tables. The extension tables are typically sparsely populated enabling the representation of the hierarchy with MIB extension tables spread across an appropriate number of MIBs to accommodate the classes required.
Although the method and apparatus described in U.S. Ser. No. 09/796,931 can provide a table-based representation of classes within a defined class inheritance hierarchy that is flexible and extensible, it is directed to the management of a collection of managed objects, each of which relates to a physical entity within that defined class inheritance hierarchy. The remains a need, however, to address, in a flexible and extensible manner, the provision of a management structure that can accommodate logical and physical managed entities, wherein the logical entities may be realized by one or more physical entries.